Declaring a Class
To design your program or code library in an object-oriented
fashion, you’ll need to define your own classes, using the class
keyword. A class definition includes the
class name and the properties and methods of the class. Class
names are case-insensitive and must conform to the rules for PHP
identifiers. The class name stdClass
is
reserved. Here’s the syntax for a class definition:
classclassname
[ extendsbaseclass
] [ implementsinterfacename
, [interfacename
, ... ] ] { [ usetraitname
, [traitname
, ... ]; ] [visibility
$property
[= value
]; ... ] [ functionfunctionname
(args
) { //code
} ... ] }
Declaring Methods
A method is a function defined inside a class. Although PHP
imposes no special restrictions, most methods act only on data within
the object in which the method resides. Method names beginning with two
underscores (__
) may be used in the
future by PHP (and are currently used for the object serialization
methods __sleep()
and __wakeup()
, described later in this chapter,
among others), so it’s recommended that you do not begin your method
names with this sequence.
Within a method, the $this
variable contains a reference to the object on which the method was
called. For instance, if you call $rasmus->birthday()
, inside the birthday()
method, $this
holds the same value as $rasmus
. Methods use the $this
variable to access the properties of the
current object and to call other methods on that object.
Here’s a simple class definition of the Person
class that ...
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